1. Field
Embodiments of the present invention relate to agricultural vehicles. More particularly, embodiments of the invention relate to methods and systems for controlling the engine speed of agricultural vehicles.
2. Related Art
Tractors and other agricultural vehicles are often equipped with speed control systems to assist operators in accelerating to and maintaining desired vehicle speeds and to maintain desired power take-off (PTO) shaft speeds. Most known speed control systems receive commands from a hand throttle, foot pedal, or other variable input device that permits an operator to manually select a desired engine speed. Many speed control systems also receive commands from a mode selector that permits the operator to select one or more pre-set engine speeds (e.g. 1,000 RPMs, 1,500 RPMs, etc.).
For safety reasons, speed control systems are typically programmed to cancel or override any pre-set engine speeds from a mode selector whenever an operator moves the variable input device. Unfortunately, this often leads to erratic and unwanted engine speed changes. For example, an operator may operate the mode control switch to select a constant engine speed of 1,000 RPM and then attempt to increase the engine speed by turning up the hand throttle or other variable input device. However, if the variable input device is currently positioned so that it calls for an engine speed lower than the pre-set engine speed, actuating it causes the engine speed to initially drop, not increase. Similarly, the operator may attempt to decrease the engine speed from a pre-set speed by turning down the variable input device, but if the variable input device is currently positioned so that it calls for a higher speed, activating it causes the engine speed to initially increase. Thus, an operator often must “hunt” for a desired engine speed by frequently moving the variable input device up and down.
Accordingly there is a need for an improved system and method for controlling the engine speed of an agricultural vehicle.